Thermostat



1944. J. w. HARRISON 2,340,056

THERMOSTAT Filed July 12, 1941 fig 1;

WITNESSES: INVENTOR fa/7n f/arr/Lian.

Patented tian. 25, 1944 John W.

THIBHOSTAT Harrison, Mansfield, Ohio, assignor to Westinghouse Electric: Manufacturing Company, East littsburgmrm, a co p ration of.

. -Pennsyl Application July 1:, 1941, Serial- No. 402,162

'1 Claims. (Cl. 200-138) My invention relates to thermostats and, more particularly, to snap-acting bimetallic strip-type thermostats.

An object of my invention is to provide a striptype thermostat which has an increasing contact pressure up until the time the cooperating contacts are disengaged.

A further object of my invention is to provide a thermostatic structure having an inherently snap-acting resilient contact-carrying member and an elongated strip bimetallic element placed in juxtaposition with respect to the snap-acting member for biasing said member to cause it to snap from one position to another.

Another object oi my invention is to provide an inexpensive, easily manufacturable thermostatic structure which has a snap-acting contactcarrying member and a bimetallic element rigidly attached thereto.

Yet another object of my invention is to proline with the adjusting screw :4 and carries a stationary contact 2. on its upper end. Said stationary contact 28 cooperates with a movable contact 32,- which is attached to the movable end portion 38 of the member II, when the thermostat is in its engaged position. A suitable terminal member 33 is attached to the adjusting screw 26 in any well known manner to aflord electrical connection therewith.

The inherently snap-acting contact-carrying 'member l4 embodies, in this instance, two exterior strips 32 and a central strip 34. The strips 32 and 34 extend longitudinally with respect to the member II and are joined at their ends by suitable, end portions 36 and 38. The exterior strips 32 are crimped or deio ed in any suitable manner which tends to reduce their length. Such strips are, therefore, .under tension while the central strip I4 is under compression. Ac-

vide an inherently snap-acting member embodying two exterior strips and a central strip joined by end portions and having a strip-type bimetallic element rigidly attached to substantially the midpoint of the central strip. v

Other objects of my invention will either be pointed out specifically in the course of the following description of my invention, or will be apparent vfrom such description.

In the accompanying drawing,

Figure 1 is a top plan view of the thermostatic structure embodying my invention, and

Figs. 2 and 3 are side elevational views of the structure shownin Fig. 1 in its closed or operated position and its open or inoperative position, respectively.

Referring to the accompanying drawing, in

which like reference characters indicate like parts in the several figures, I show a thermostatic structure It embodying a supporting structure I2, an inherently snap-acting contact-carrying member i4 and a bimetallic element It rigidly attached thereto.

The supporting structure l2 comprises, in this instance, an elongated substantially rectangular plate-like base. An upstanding pedestal I8 is located at one end of the base and is rigidly attached thereto in any suitable manner. The pedestal I8 is adapted to retain the contact-carrying member I4 and the bimetallic element ll above the base I2 and substantially parallel thereto, as hereinafter described. An upwardly extending inverted L-shaped bracket 20 is rigidly attached to the supporting structure l2 at its second end by means of suitable screws 22. The

bracket 20 receives an adjusting screw 24 in its upper portion, which is adapted to engage the movable end portion 38 of member M, as hereinai'ter described. A second adjusting screw 2 is threaded through the supporting structure l2 relatively close to the bracket 2| substantially in cordingly, the member It will be normally curved, say, in a concave downwardly manner, as shown in Fig. 2, with the central strip positioned substantially above the two exterior strips 32, so that the member M will move from one position to another with a snapping action, in a well.

known manner. One end portion, namely portion 38, is rigidly attached 'to the pedestal I! by means of a suitable set screw 40, while the sec ond end portion 38 has the movable contact 3|! attached thereto and movable therewith. With the member attached at one end to pedestal II and being positioned concave downwardly, as an externally applied force is directed against the central strip, the strip will tend to straighten until said central strip just passes beyond its midpoint, at which time the movable or free end portion 38 of member It will move upwardly with a snap action.

The movable contact 30 rigidly attached to movable end portion 38 or member 14 will thus become disengaged from the stationary contact 28 with a snap action. However, it follows that as the exterior force is applied to the central strip 34 and up and until the instant of snapping, the

' stance, an elongated strip-type element which has substantially the same width as the central strip 34 of member I4, and a length slightly greater than one-half that of said member I. In addition, if it be desired, the stationary end of the element I may be broadened to be substantially equivalent to the width or the stationary end portion 36 of member ll, as shown in Fig. 1. The

so element it may thus be positioned directly upon the "member i4 whereby its stationary end portion will substantially cover the stationary end portion 38 or member I4 and the main portion of the element It will fit directly over the central strip of member l4. The element l6, positioned upon the member H in such a manner, is then rigidly attached to the supporting structure l2 by means of the set screw 40 and the pedestal l8 and is located in juxtaposition with respect to the upper surface of the member l4. The free or movable end of element I6 extends slightly beyond and is rigidly attached to substantially the midpoint of the central strip 34, say by spot welding, or the like at point 35, so that the central strip 34 will move with the element I6 as it flexes in response to its change in temperature.

It, therefore, follows that the thermostat embodying my invention, including the bimetallic element 16 rigidly attached to substantially the midpoint of the inherentlysnap-acting contactcarrying member, will be snap acting in character even though the thermal responsive element thereof be merely an elongated strip-type bimetallic element.

When operating, the thermostat embodying my invention and assuming such thermostat to be in its closed or operated position (see Fig. 2), the cooperating contacts 3|! and 28 are engaged. As the bimetallic element l8 increases in temperature, the free or movable end of said element will flex downwardly in a clockwise direction.

The mid-portion of the central-strip 34 of contact-carrying member l4 will then be likewise bodily moved downwardly. Said downward movements will continue until the central strip 34 is substantially at its, midpoint or neutral plane. During this time, the pressure between the movable contact 30 and stationary contact '28 will increase. However, as the central strip 34 reaches its midpoint, the member M will, in a well known manner, instantly snap to its upper or contactdisengaged position, (see Fig. 3) at which time the movable free end 38 of member l4 will engage the adjusting screw 24. This action thus breaks the circuit through the thermostat l0.

Then as the bimetallic element [6 decreases in temperature, said element will flex in a counterclockwise direction. The central strip 34 of member I4 will then, due to its being rigidly attached to the free end of element l6, be likewise moved upwardly. This action will continue until said strip reaches its midpoint, whereupon the movable contact 30 will snap downwardly to its contact engaged position.

It, therefore, follows that the creeping or slow moving action of the element I8 due to its intimate association with the member l4 and to the fact that it is rigidly attached to substantially the midpoint thereof, ;will cause the contactcarrying member l4 to move from one position to another with a snap action.

The adjusting screw 24, which limits the upward position of the movable end portion 38 of member l4, may, therefore, be employed to readily adjust the closing or downward movement of said member, while the adjusting screw 26 which carries the stationary contacts 28 may be readily adjusted to vary the opening temperature of the thermostat.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, bin is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are specifically set forth in the appended claims.

I claim as my invention:

1. A thermostat comprising, in combination, an inherently snap-acting contact-carrying member having only one point of support, and a bimetallic element rigidly attached near one boundary of said member for controlling and moving in unison with the movements thereof.

2. A thermostat comprising, in combination, an inherently snap-acting contact carrying member, embodying three longitudinally extending strips, comprising a central strip and two exterior strips, and a bimetallic element attached at one end to substantially the midpoint of the central strip for actuating the movements of said member.

3. A thermostat comprising, in combination, an inherently snap-acting contact-carrying member, embodying three longitudinally extending strips, comprising a central strip and two exterior strips, and a bimetallic element attached at one end to substantially the midpoint of the central strip for actuating the movements of said member, said element being substantially the same width as the central strip of the member and positioned in juxtaposition therewith.

4. A thermostat comprising a supporting structure, an elongated inherently snap-acting contact-carrying member having two exterior and a central longitudinally extending strip and two end portions joining the ends of said strips, a bimetallic element positioned upon said central strip, and means engaging one end portion of the contact-carrying member and bimetallic element for rigidly attaching them to the supporting structure, the second end of the element being rigidly attached to substantially the midpoint of the central strip to bodily move said strip in response to variations in the temperature thereof.

5. A snap-acting strip-type bimetallic thermostat having a supporting structure, an elongated inherently snap-acting contact-carrying member and an elongated bimetallic element rigidly attached by one end thereof to substantially the midpoint of the member, and means for rigidly attaching said element and member to the supporting structure whereby as the element flexes in response to the changes in temperature thereof it will bodily move said member to its snapping point after which time said member will move the element.

6. A thermostat comprising, in combination, a snap-acting contact-carrying member and a bimetallic element attached thereto, said element moving in one direction toward the center of the snap-acting member upon increase in temperature whereby upon a predetermined amount of said movement the contact-carrying member will snap in the opposite direction, and upon cooling said bimetallic element will return toward its original position and toward the center of the contact-carrying member a second predetermined distance whereby said member will snap to its original position, moving in a direction opposite to that of the bimetallic element.

7. A thermostat comprising, in combination, an inherently snap-acting member having its sole point of support at one end and carrying a contact at its other end, and a bimetallic element rigidly attached at said point of support for controlling and moving in unison with the movements of said member.

JOHN W. HARRISON. 

